Hydrofluoroolefins (HFOs) represented by the formula: CF3(CX2)nCF═CH2, the formula: CF3(CX2)nCH═CHF, and the like are useful compounds as, for example, various functional materials, solvents, refrigerants, foaming agents, monomers for functional polymers or starting materials of such monomers. For example, HFOs are used as monomers for modifying ethylene-tetrafluoroethylene copolymers.
Of the above HFO compounds, CF3CF═CH2 (HFO-1234yf), CF3CH═CHF (E-/Z-)(HFO-1234ze), and CF3CF═CHF (E-/Z-)(HFO-1225ye) have recently gained attention as they offer promising prospects as refrigerants with low global warming potential (GWP).
As an example of methods for producing the HFO compounds represented by the formulas above, a method has been reported in which a chlorine-containing alkane or chlorine-containing alkene starting material having the same number of carbon atoms as that of a target fluoroolefin is reacted with a fluorinating agent, such as an anhydrous hydrogen fluoride, in the presence of a catalyst (see, for example, Patent Literature (PTL) 1).
However, HFO compounds, which contain a double bond, have low stability, compared with hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), and the like, which have been used as heat transfer media (refrigerants). Therefore, for example, an HFO compound when used as a heat transfer medium for an air-conditioning system may react with entrained air or oxygen, may react inside the air-conditioning system with a part or parts that are in contact with the heat transfer medium, or may result in decomposition of the HFO compound itself, depending on the operating conditions. In these cases, the performance of the air-conditioning system problematically decreases; thus, an improvement in the stability of the HFO compound is necessary.
Although the performance of air-conditioning systems has been improved in accordance with an improvement of the systems, there is a limit to improving the performance with the improvement of the systems, and an attempt has been made to improve, for example, the refrigerating capacity by adding an additive to an HFO compound used as a heat transfer medium.